<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon">E</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">A</font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">E</font>;<br/><b>let </b><font color="Maroon">B</font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">E</font>;<br/>





<b>assume </b><a NAME="E1:49"/>
for <font color="Olive">x</font> being   <a href="subset_1.html#M1" target="_self">Element</a> of <font color="Maroon">E</font>  holds <br/>( ( <font color="Olive">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">A</font> &amp; not <font color="Olive">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">B</font> ) or ( <font color="Olive">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">B</font> &amp; not <font color="Olive">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">A</font> ) )
 ;<br/>

<a NAME="E2:49"/><b>then </b>
for <font color="Olive">x</font> being   <a href="subset_1.html#M1" target="_self">Element</a> of <font color="Maroon">E</font> holds <br/> ( <font color="Olive">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">A</font> iff not <font color="Olive">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">B</font> )
 
;<br/>
<b>hence </b><a NAME="E3:49"/>
<font color="Maroon">A</font> <a href="hidden.html#R1">=</a> <font color="Maroon">B</font> <a href="subset_1.html#K3" target="_self">`</a> 
 <b>by </b><i/>;<br/>


</div>
